feat: reorganize model dirs and separate concerns better within the models

[Samlant]

Description, issue

Some models lack a clear separation of concerns and often levy too much work onto the Presenter, which should have a much more concise role in the program; namely to receive, serve and coordinate between the models & views.

Solution

Divide the models into smaller, clearer modules that share similar roles/tasks. A restructuring of dirs is to be expected, along with the creation of many smaller, specific modules.